Help, please, with overexposed areas on film strip

[snark]

I shot a roll of Tri-X with an AE-1. About one third of the frames had dark areas covering part of the image. I changed batteries and shot a test roll at various shutter speed and aperture combinations, which turned out fine. A few days later I ran another roll through the same camera. Again, dark areas vertically across about half the frames. I scanned a representative portion and it is attached.

Now I am not sure whether this is a problem with the camera or the developing. Note how the dark (overexposed?) areas get progressively darker. On some frames

the dark areas extend to the outer edges of the film and seem to correspond with the perforations.

My developing practices are uniform, stainless steel reel and tank, Diafine at 75F for three and a half minutes.

Any thoughts on what's causing this and how to correct it? My best guesses are light leak (but why not evident on all frames?) or shutter curtain hanging up.

 

[480sparky42 41]

Light leaking in through the seals on the back of the camera.

 

[compur]

Yes, looks like light leaks. To be sure you can test by applying opaque tape covering edges of film door and shoot another roll.

 

[snark]

Okay, light leak is the consensus. That the fogging was so prominent on some frames and practically nonexistent on others may have something to do with pressure inadvertently applied to the film door during use?

I will replace the foam seal and see how it goes.

Thanks, guys.

 

[480sparky42 41]

Light leaks will vary because 1. the time each frame spends against the pressure plate varies and 2. the brightness of the light the camera is exposed to varies.

If you take a quick succession of images in low light, the fogging won't be as pronounce as shooting in sunlight and taking your time snapping the shutter.

 

[Derrel]

The film is wrapped fairly tightly on the film take-up spool...this is what causes the uneven light leak patterns.

 

[Derrel]

Note how frame 1 has much less light leak darkening than frame 5....frame 1 is/was covered up by three layers of film...

 

[JBPhotog]

Two potential issue to check.

1. Load a roll of film and set the camera at its highest shutter speed 1/1000 and stop the lens down to f16 or f22 with the lens cap on. In bright sun hitting the camera back, take a few shots then process that short strip. If the camera light seals are original they likely have compressed and deteriorated to the point of failure, your processed film will then that story.

2. The AE-1 had a cloth focal plane shutter curtain. One simple way to rule out a malfunctioning shutter curtain is to cut a piece of white paper just big enough to rest on the film guides but cover the opening where the film would be exposed and close the camera back. Take the lens off, attach a flash with a long enough sync cord and aim it at the lens mount. Fire away at different shutter speeds, what you should see is one curtain following the second curtain without hanging up or dragging displayed by a white strip or full frame if the shutter is set to a slow speed. BTW, this is also a great way to check flash sync speeds. Additionally you can set the camera up without a lens, point the flash at the lens mount, open the camera back and only look at the actual curtain when you trip the shutter. If there is any light leaking through the curtain you should see it.

 

[480sparky42 41]

T......... One simple way to rule out a malfunctioning shutter curtain ...........

How could a malfunctioning shutter cause exposure on the edge of the film that's outside the frame?

 

[JBPhotog]

T......... One simple way to rule out a malfunctioning shutter curtain ...........

How could a malfunctioning shutter cause exposure on the edge of the film that's outside the frame?

Easy, if the shutter stays open long enough the exposure blooms past the frame edges, seen it a hundred times.

 

[480sparky42 41]

T......... One simple way to rule out a malfunctioning shutter curtain ...........

How could a malfunctioning shutter cause exposure on the edge of the film that's outside the frame?

Easy, if the shutter stays open long enough the exposure blooms past the frame edges, seen it a hundred times.

Even to the sprocket holes on adjacent frames?

 

[JBPhotog]

T......... One simple way to rule out a malfunctioning shutter curtain ...........

How could a malfunctioning shutter cause exposure on the edge of the film that's outside the frame?

Easy, if the shutter stays open long enough the exposure blooms past the frame edges, seen it a hundred times.

Even to the sprocket holes on adjacent frames?

He is using Tri-X, ISO400 so yes, it is possible.

The point is and was, do some testing to determine the issue.

 

[480sparky42 41]

T......... One simple way to rule out a malfunctioning shutter curtain ...........

How could a malfunctioning shutter cause exposure on the edge of the film that's outside the frame?

Easy, if the shutter stays open long enough the exposure blooms past the frame edges, seen it a hundred times.

Even to the sprocket holes on adjacent frames?

He is using Tri-X, ISO400 so yes, it is possible.

The point is and was, do some testing to determine the issue.

Explain the dark spots between the sprocket holes between frames 5 and 5A with a malfunctioning shutter.

 

[JBPhotog]

T......... One simple way to rule out a malfunctioning shutter curtain ...........

How could a malfunctioning shutter cause exposure on the edge of the film that's outside the frame?

Easy, if the shutter stays open long enough the exposure blooms past the frame edges, seen it a hundred times.

Even to the sprocket holes on adjacent frames?

He is using Tri-X, ISO400 so yes, it is possible.

The point is and was, do some testing to determine the issue.

Explain the dark spots between the sprocket holes between frames 5 and 5A with a malfunctioning shutter.

When all you have is a hammer, everything looks like a nail.

 

[480sparky42 41]

T......... One simple way to rule out a malfunctioning shutter curtain ...........

How could a malfunctioning shutter cause exposure on the edge of the film that's outside the frame?

Easy, if the shutter stays open long enough the exposure blooms past the frame edges, seen it a hundred times.

Even to the sprocket holes on adjacent frames?

He is using Tri-X, ISO400 so yes, it is possible.

The point is and was, do some testing to determine the issue.

Explain the dark spots between the sprocket holes between frames 5 and 5A with a malfunctioning shutter.

When all you have is a hammer, everything looks like a nail.

No hammer or nail. Just a malfunctioning horizontal-traveling cloth focal plane shutter and an excess of photons.